This invention relates to a shearing mechanism and more particularly to an apparatus for severing a material mass with a pair of shears rotating about a pivot.
Conventional shearing devices have a top and bottom shear or jaw each with cutting surfaces. At least one of the shears pivots about a transverse connecting pin and cuts the material placed in between the shears. Typically applications for these devices are for demolition to clear and reclaim rubble.
A drawback with many devices of this type is that when one shear is pivoted towards the second shear to cut the material, the shears tend to separate. This separation often results in warping rolling and/or breaking of one of the shears and the connecting pin, thereby limiting the material that can be crushed as well as the life expectancy of the shear.
Examples of shearing devices that have tried to alleviate shear separation are described in U.S. Pat. Nos. 4,543,719, 4,558,515, and 4,776,093. These devices attempt to solve the problem associated with shears separating by providing a second parallel, non-cutting shear adjacent a first non-movable or fixed shear. The movable shear then crushes the material between the second non-cutting shear and the fixed shear. However, a drawback to these devices is that the material may often lodge in between the first shear and the second shear and must later be pushed out resulting in an interruption of the cutting operation. Further these shearing devices waste available cutting force because the force of the moving shear is directed into deforming or dragging the material mass against or through the non-cutting or second shear and the first non-movable shear.